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UltravioletPhotography

Discussion on cameras and lenses for UV


colinbm

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Comment by nfoto (Admin): This topic is established as a placeholder for the various technically orientated post in the Felicia thread here http://www.ultraviol...ible-and-uv-a/.

 

To achieve a continuity in the thread, I've taken the liberty of copying the second and third post in that thread into this one.

 

 

 

Here is the comment by colin on Igoriginal's Felicia images.

 

Very nice images & processing Iggy.

I like the highlight of the petal damage here too.

How have you controlled the excess UV/Blue from the S8612 filter in the Visible shot Please ?

Col

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Thanks for the kind words, colinbm!

 

Good question.

 

Note the white-balance setting that I listed in my data under the "Visible" photograph.

 

("White balance set to default 'FLASH' mode").

 

In other words, I have discovered that by setting white balance to the camera's preset "flash" setting (in the camera's preset white balance options menu), while keeping the flash turned off, the RGB scheme / distribution of the Bayer Array sensor shifts the spectral bandwidth slightly towards the red-end, and thus compensates (somewhat) for the blue-end shift created by a filtered-on Schott S8612 glass (since Schott S8612 aggressively clips off some red-end light transmission, at the 680 to 700nm line, and of course all bandwidths past that. And, especially Schott S8612 that is custom cut to *2mm thick*, or greater, the light transmission intensity curve even begins to taper off at 600nm!).

 

And this makes sense, because the preset "flash" white balance option within the modern DSLR is also designed to off-set the blue-end domination caused by the built-in flash of the camera (built-in camera flashes typically fire at 5,000 to 7,000 kelvin color temperature ... particularly more smaller, compact / mirrorless models with under-powered pop-up flashes).

 

So, try it with your camera. When using Schott S8612 (which is more aggressively inhibitive of the twilight fringes of red-end light crossing into near IR, compared to BG38, 39, and 40), set your white-balance to the existing / factory preset "flash" menu option, while keeping your pop-up / built-in flash closed or turned off when you take your exposure.

 

Now, I am not saying that the preset "flash" white balance will COMPLETELY restore all red-end tone loss. And not all camera preset white balance modes elicit the same exact Bayer response to light. They can vary, to some extent, from model to model.

 

But ... at least for the micro-four-thirds systems that I most often use (Panasonic G / GH / GF series cameras, converted to Full Spectrum), the preset "flash" white balance mode makes an appreciable difference, and puts a noticeable dent in the blue-end shift of Schott S8612. Enough to restore oranges and reds to a NEAR-convincing balance. And certainly enough to make any additionally subtle color compensations, in PP, without degrading the image too much (even a JPG image).

 

And the point of this discovery has spared me from the extra step of having to fumble around with swapping out my S8612 with a BG glass, every time I want to do a "Visible" shot of a specimen before screwing on the UV-pass glass on top of the IR cut glass. No more having to carry additional BG glass in the field! Just leave your Schott S8612 on, at all times ... both "Visible" shots, and UV-stacked shots alike! ;)

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You could easily mount the filter pack in an exchangeable unit, using say a K3 ring on the lens and K2 to hold the filters, Then you have a bayonet mount so swapping filters is a split-second affair. Provided you are careful you won't even need to twist the K2 so it locks thus avoiding the need for pushing the unlock tab when you want to get the filter off.

 

I'm sure the S8612 is an excellent IR-cut filter, but there is always the danger of additional filters encroaching on the UV transmission of the filter stack as a whole. Thus at the very least one should try if using single filters such as a Baader alters the overall UV response to the better. When the Baader is mounted in a K2 there is no added handling overhead incurred.

 

A final note on setting w/b for UV. The Panasonics in general can get a surprisingly well balanced and pretty neutral UV response over the entire UV range covered by the camera/lens if you use in-camera w/b setting against a white (or grey) PTFE sample. I'm using this approach for shooting UV video all the time. However, even better can be had if you add more targets with neutral characteristics and different spectral reflectance and take the extrra steps to build a profile in a RAW editor.

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Thanks very much Iggy, I have much to learn, but I understand now what you are doing.

With the C-mount lens, the image circle must be small....does the 5mm macro ring increase the image circle, does it fill the 4/3rds sensor now ?

Cheers

Col

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@ Fierce Bear:

 

Yes, a single filter like the Baader-U is surely superior, instead of stacking two filters to obtain similar UV-A transmissions. However, I do not feel comfortable with taking a $300 filter into the field (outdoors / nature), and risk cracking or chipping it. It's not worth the risk for me, given my limited income. Especially since many of my outdoor / field shots involve a lot of hiking along winding trails, dirt roads, slippery rocks, streams, steep hills, etc. Not worth the risk of "accidents." I would only reserve the use of a Baader-U filter for the safe and controlled confines of indoor shooting, only ... where I would not be at the mercy of the harsh elements. Hence, a single piece of glass, for $300, is not worth the risk for me ... when stacking a cheaper UV-pass glass (U-360 or U-340) with Schott S8612 has given me very similar results to a single Baader-U. And for my limited finances, a U-360 or U-340 is more cost-efficient. If those filters break (from accidental slip, trip, bump, or knock, while outdoors in nature) it would cost 1/4 to 1//2 the price of a Baader-U, to replace. But, this is just MY preference, and MY comfort level, of course. :-) Everybody has their own preferences and comfort levels, no doubt (and their own financial capabilities, as well, in replacing damaged equipment). I, personally, only reserve my Baader-U for indoor UV photography (in a more controlled environment). It's just not worth risking in the wild outdoors, since a U-360 / U-340 stacked with a Schott S8612 has given me almost comparable results. In fact, when stacking 1mm to 1.5mm-thick U-340 with 1.5mm thick S8612, I have not seen much difference in overall image results to a single Baader-U. They are very close in the image yield / UV "color" representation. (Although, admittedly, where I notice that the Baader-U actually excels compared to my stack, is in exposure times.)

 

As for white-balancing for UV-only shots ... yes, I already employ a small block of virgin-white PTFE for in-camera white-balancing for UV-only photos (see my data under the UV shot of the Felicia amelloides. It is already listed as such, for my UV white-balancing). However, what Colin and I were discussing was not white-balancing for UV shots, but how to obtain better color representation when shooting VISIBLE-spectrum shots using S8612, so the images are not overly-dominated by blue-end shift. In order words, how to restore some of the loss of red-end colors in-camera, which the S8612 tends to clip.

 

@ Col,

 

The image circle on the Wollensak Velostigmat 25mm F/1.5 Cine / C-mount lens is large enough to completely cover the Micro-4/3 sensor. Even when I used as many as 4 macro rings stacked together (5mm each, for a total of 20mm extension), I still saw no image fall-off around the edges! So, this lens is truly a gem. And the fact that I have discovered it to have very deep UV-transmissive properties is why I now use this lens, in place of Kuribayashi / Kyoei 35mm for wide-angle shots on my Micro-4/3 systems.

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For visible work, use the CC Passport and make a session profile with PhotoNinja., You'll get superb colour rendition this way. Much easier than any ad hoc makeshift approach.

 

Andrea has cracked a Baader U in the field, I never got around to achieve the same despite deploying several of them at time. Guess their longevity is a random variable with unknown expectation. In doors you can trip on a flash cable or similar and wreck your gear too. So no place is to be considered safe as long as a photographer is present.

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With a Lumix cam, I wonder if you can white balance through the S8612 ?? We need to try that experiment.

 

The colour in the Visible shot above is fairly good. There's still a bit too much blue in the grass, but you could prolly shift the colours a bit more in the editor and tone down a bit of the blue ??

 

Restoring Visible colour in broadband cameras is a tricky business, and, interestingly, white balance settings alone do not always completely put colours right. The colour profiling in Photo Ninja has - so far - given me the best colours. Although there are still some scenes which show some bits of incorrect colour, so I continue to experiment.

 

***

 

Indeed, I managed to shatter a Baader-U in the Sonoran desert. Don't know how I did that !! I must have stepped on it or put a tripod leg on it not realizing that it had fallen on the ground. Somewhere there is a photo here on UVP of the sharp shards of that poor filter. I didn't want to leave it in the dirt for animals or people to step on and maybe get cut.

 

A couple of my Baader-Us are now showing a little wear by way of very minor scratches on the surface. So far there seems to be no hit on the photo quality from them.

 

Some of the BG glass or the S8612 can eventually show deterioration from oxidation, so it is very important to keep those filters cleaned and properly stored after use. I saw some problems with one of the BGs after about 2 years, but was able to clean it up with no permanent damage yet. So it is not clear which filter set is the most economical in the long run. We shall see!! ;)

 

Nothing is easy - or particularly inexpensive - in the UV game it would seem.

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@ Fierce Bear:

 

Thank you for your suggestion of looking into 'PhotoNinja.' I've heard of it, but haven't given it a try, yet. I am glad that you brought it up. It's a good to-do reminder. Thanks!

 

However, it should be pointed out that when you shoot with a mirrorless system that has full-time live view (through the sensor) and through-the-lens custom white-balancing, I haven't had the need to worry about correcting colors in PP all that much, compared to mirror-based (single lens reflex) systems. The micro-4/3 systems have a VERY ROBUST custom-white-balancing algorithm, via steps taken through the EVF, which many other mirror-based DSLRs cannot rival in the range of white-balancing range, in-camera. (We are talking about the "shoot the target to set the custom white balance" option, here. VERY robust). I just haven't done any in-camera custom white-balancing through S8612, yet. But I will experiment.

 

And, yes. Indeed, you are correct, that NO photographic environment is 100% safe. ;) However, there are MANY more variables in the field, than in a controlled lab. I'll take my chances with keeping my ONLY copy of a Baader-U in my lab for the time being, instead of hitching it along for a ride into the wild. There are no hailstorms, swooping birds, charging animals, wind-swept sand, fire ants, wasps, and other uncertainties within a more controlled environment (all other factors remaining equal, since a clumsy photographer is still a clumsy photographer, whether indoors or outdoors). However, you CAN'T control what is NOT an extension of yourself. Even if you try. So, like I said: It all boils down to what you are comfortable with. Having cracked filters before, after running through the woods from a hornet's nest that I accidentally disturbed, I will just stick with my cheaper filter-stacking in the field, thank you. ;)

 

 

@ Desert Dancer:

 

Yes, indeed. I am quite CERTAIN that it is possible to obtain more accurate-looking colors, if employing the "take snapshot to set custom white-balance to target" option of these M-4/3 systems. This is truly an unrivaled and ROBUST system of in-camera custom white-balancing, as said above to Fierce Bear. It is very similar to the "click to white-balance" tools, in PP. The Panasonic M-4/3 systems can do it quite well, with no need for PP white-balancing. So can the Olympus M-4/3 systems. And I have just confirmed that the Pentax K-01 mirrorless APS-C system is also quite robust in its in-camera set-to-target custom-white balancing! (After having a Pentax K-01 mirrorless APS-C camera converted to Full Spectrum / Astrophotography grade).

 

But, let me explain why I have not yet tried to SET any "set-to-target" custom white-balancing, in my Panasonic ... and instead, have resorted to the cruder preset / factory "flash" white-balance option: You see, I do a lot of work in both, UV and Infrared alike, and so, I have those two custom white-balance memory spots (in the Panasonic models) already taken up. That is to say, that custom white-balance memory slot #1 is set to PTFE (for UV work), and custom white-balancing memory slot #2 is set to green grass, for IR work. I therefore didn't want to disturb those memory slots. And Panasonic only has TWO custom white-balancing memory slots. Which is still MORE than most other systems (which only have ONE custom white-balance memory slot).

 

Regardless, though, you can say that I have just not wanted to mess with the custom white-balances which I have saved, in-camera. But I concur that this is mostly pure laziness, and not much else, since "set-to-target" custom white-balancing is NOT that time consuming, after all. What a BUM I have been. Hah!

 

But, then again: I have three full-spectrum-converted Panasonic models. So, why not just devote ONE of them to UV and Visible custom white-balancing, and use another model of IR work? That way, I can save both - PTFE-balanced and S8612-balanced profiles, in both memory slots of the one camera.

 

Hmmm. B)

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By the way, Desert Dancer ... S8612 can indeed become oxidized over time. Surface ("film") oxidation, however, can be easily polished off, using the correct polishing mix. All without scratching the glass.

 

BG40, on the other hand, doesn't oxidize, from what I understand. Not sure about BG38 or 39, though. They could be of slightly different composition, compared to BG40.

 

And some UV glass can become SOLARIZED over time. However, unlike mere surface oxidation which can be polished off ... some types of solarization is "burned in", and can become permanent (with the exception of being treated early on, through industrial high-heat treatment. Ex: "thermal bleaching" processes), otherwise, which would then require the eventual replacement of the filter.

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Oh, so the GH2 has 3 custom white-balance memory slots? Very nice!

 

No, I curently own a G2, a G3, two G5's, and a GF3 in my arsenal. My G2, one of the G5's, and the GF3 are the full-spectrum converts. I once had a GH1, but never held on to it long enough to check out its menu. It had some bad electrical faults that needed repairing, and so I sold it for parts.

 

But, no. I wasn't aware that the GH2 had 3 memory slots for CWB. Wow. I just may have to look into that. Perhaps sell my somewhat "outdated" G2 (even though it is full-spectrum converted), and use some of that credit toward a GH2. But then, I've spent a lot this past year to acquire gear, so I am not in spending / acquisition mode, right now. I am in recoup mode. Haha.

 

Then again, I really like the G2 and the way it feels in the hand ... thus, not so willing to part with my first baby. Only recently has Panasonic returned to giving their mid and upper-range models the proper DSLR-like chunky hand grip (like the G5, onward) which I love so much. (The G3 was a total error in marketing judgement, in terms of body re-design!)

 

Jeeez. Thanks for giving me yet another "itch" to acquire yet ANOTHER Panasonic model. Hah. :-P

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The GH-2 has three separate slots on its mode dial labelled C1-C3, respectively. So you can store three different sets with w/b combined with any other shooting setups you like to be able to switch rapidly to. I'm allocating C1 to UV (with Baader), C2 to IR (with Wratten 87C or equivalent), and C3 for visible light with Baader UV/IR Cut filter.

 

One might even argue there actually are *4* slots as the current settings of the camera are activated when you switch away from the C1-C3 positions. In fact, for the GH-2 dedicated to video I avail myself of this to set a UV video baseline as the default. The other GH-2 is only used for stills and has a permanently attached Coastal Optics 60 mm f/4 APO lens on it. The Baader here is rear mounted (inside the mount adapter) so unlikely to break even when the camera sees hard field use.

 

Although the w/b in-camera for UV is very good to excellent when you set it against a UV-neutral target, even better results can be had with additional processing in PhotoNinja.

 

Last but not least one should never overlook the fact that a 'neutral' w/b in UV can only be achieved if the filtration allows a sufficient wide band of the UV to pass through it. Once you start using narrow-band UV filters, this condition is no longer met and you cannot get the white or grey hues any more.

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The GH-2 has three separate slots on its mode dial labelled C1-C3, respectively. So you can store three different sets with w/b combined with any other shooting setups you like to be able to switch rapidly to. I'm allocating C1 to UV (with Baader), C2 to IR (with Wratten 87C or equivalent), and C3 for visible light with Baader UV/IR Cut filter.

 

One might even argue there actually are *4* slots as the current settings of the camera are activated when you switch away from the C1-C3 positions.

 

Ahhh. I didn't know that each 'C' (custom) position on the mode dial provides yet ANOTHER set of the same 2 available memory slots of custom white-balancing saving! This is awesome! In that case, what you REALLY have on your GH-2 is EIGHT total custom white-balancing memory slots! (C1 x 2 CWB slots) + (C2 x 2 CWB slots) + (C3 x 2 CWB slots) + (non-C mode x 2 CWB slots) = 8 CWB memory slots!

 

And since my Panasonic G5 has two 'C' modes (C1 and C2) on the mode dial, then that means that I have *SIX* total CWB memory slots, and NOT just the two that I previously assumed! This is great! Thank you for bringing that to my attention! I suppose I should start paying attention to the usefulness of OTHER positions on the mode dial (and how they can enhance / aid my work), rather than habitually always shooting in 'M' mode like it's the only mode on my camera. :P

 

The other GH-2 is only used for stills and has a permanently attached Coastal Optics 60 mm f/4 APO lens on it. The Baader here is rear mounted (inside the mount adapter) so unlikely to break even when the camera sees hard field use.

 

Last but not least one should never overlook the fact that a 'neutral' w/b in UV can only be achieved if the filtration allows a sufficient wide band of the UV to pass through it. Once you start using narrow-band UV filters, this condition is no longer met and you cannot get the white or grey hues any more.

 

Agreed. however, YOUR version of "wide band" may not be OTHER people's version of "wide band." While it's true that some more exotic and UV-dedicated lenses made of quartz-fluorite (such as 'Coastal Optics') will permit for a much wider bandwidth of transmission (down to roughly 300nm, and some more EXOTIC models down to upper 200's nm range, from what I have read!), that doesn't mean that everyone has access to (or can afford) such lenses. And if someone is working with the limiting factor of NON-uv dedicated lenses (of which their discovered UV-transmission properties are mere accidents or unintentional consequences of various production designs of simple element configurations), then it doesn't really matter if you place a higher-quality, expensive piece of UV glass like the Baader-U in front of such a lens, because the LENS will truncate (clip off) the broader transmission bandwidth of the more dedicated and specialized UV-pass filter. Hence, the lens will be the LIMITING factor, and not the choice of filter.

 

For instance, with my current budget, I could only afford to do UV work with cheaper El-Nikkor enlarging lens (mounted on focusing helicoids), the Kuribayashi / Kyoei preset-aperture lens variants made in the early 1960's, or other make-shift non-dedicated *accidental* UV-transmissive lenses. Often, these "regular" (non quartz-fluourite) lens have a UV transmission cut-off around 340nm. And sometimes, perhaps can usefully transmit down to 325nm at best, with enough exposure time and sufficient energy from a clear-day sun.

 

So, what does it matter if I use a much BROADER bandwidth UV glass, if my LENS is the limiting factor? If the Baader-U transmits down to roughly 300nm, what does that matter if an El-Nikkor 80mm F/5.6 can only transmit UV down to about 340 or 330nm? If the LENS truncates the bandwidth, then any additional bandwidth advantage from a more expensive and dedicated UV-pass glass is lost and blocked out.

 

For the record, my current budget limits me to work with cheaper, non-dedicated "UV accidents" ,.. such as El-Nikkor enlarging lenses, Kuribayashi / Kyoei variants, and my newly-discovered Wollensak Velostigmat 1/2" (25mm) F/1.5 Cine lens, which I believe transmits to about 330nm or so. I can probably squeeze out as much useful UV bandwidth as down to 325nm, on a good day. :rolleyes: But, no much further than that. And typically, 340nm is the bottom-most norm, for many of the cheaper "UV accidents" of the 1940's through 1960's preset lenses for "regular" photography (before UV-blocking multi-coatings began to be used, in the late 60's / early 70's). Yet ANOTHER reason why a U-340 or U-360 really is ENOUGH, for such non-dedicated glass. Baader-U would be moot (and financially frivolous), because it would be handicapped by the lens, below 340nm.

 

Now, maybe one fine day, I could afford to invest in a multi-thousand-dollar, dedicated quartz-fluorite lens for this HOBBY. But, as it stands for now (based on my currently limited finances), I have to be realistic and invest mostly in the photographic gear that pays my bills. That being: Event photography (weddings, modeling, product / marketing, athletics / sports, portraiture, etc.)

 

I hope that changes, though. Here's hoping. ;) You CAN see, though ... based on my photo above, that a stacked U-360 / S8612 provides sufficient enough bandwidth to obtain UV-neutral greys and whites. :)

 

(However, you have truly given me some USEFUL ideas, now that I am aware that the 'C' mode positions provide yet MORE sets of CWB memory slots. 2 CWB positions, per 'C' mode. This is great news! Thanks so much!)

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Here is the approximate transmission bandwidth of stacking U-360 (2mm thick) with S8612 (1.5mm thick), supplied to me by a trusted merchant / supplier. It's the same stack that was used to obtain the above-posted UV photo of Felicia amelloides.

 

You can see that there is PLENTY of sufficient UV-bandwidth to elicit enough UV greys and whites. True, it's no Baader-U ... but it's a perfect fit for most non-dedicated (non quartz-fluorite) lens which can only transmit useful amounts of UV down to about 340, or perhaps even 325nm at best. Baader-U would therefore be a MOOT indulgence, on non-dedicated lenses.

 

http://i.ebayimg.com/00/s/MzkyWDgwMA==/z/E5oAAOxybqpRgNWy/$T2eC16NHJHYFFj-!BHW8BRgNWyYd(!~~60_3.JPG

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We rely on the spurious out-of-passband transmission for the dyes in the Bayer matrix to make our false UV colours and hence the UV "white" or "grey". Meaning, within the passband of the used filters (and lens), there must be at least 2 preferably 3 cross-over points in the transmission curves of these dyes. Fortunately, in the upper UV-A >=340 to

 

The UV response of the Baader may not appear very different from other alternatives (incl. filter stacks) unless you view it on a log not linear scale. And being a single filter it does increase any focus shift to a lesser degree Plus there is the not entirely unimportant question of exposure time. I'm living in a Nordic region in which UV levels are fairly low so getting the most of what little UV is present the filter has its merits. On a good day I can even do UV handheld when a Baader U 2" is used.

 

It is true this filter is expensive. But when it can give you many years of service, the price is more agreeable. For an m43 camera in which you always use dedicated mount adapters, mounting the filter inside the adapter makes it far less prone to damage so its longevity is enhanced.

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We rely on the spurious out-of-passband transmission for the dyes in the Bayer matrix to make our false UV colours and hence the UV "white" or "grey". Meaning, within the passband of the used filters (and lens), there must be at least 2 preferably 3 cross-over points in the transmission curves of these dyes. Fortunately, in the upper UV-A >=340 to <400 nm we normally see this requirement fulfilled even with non-specialized UV lens candidates.

 

 

This is all true. Myself being involved in the ongoing research in physics, including the universal forces (electromagnetism, gravity, nuclear, etc.), I have come to realize that when it comes to electromagnetism: As the energy of photons increases (due to the increased frequency of the wave-forms that they "ride" on, which results in shorter wavelengths), it takes less bandwidth in order to complete another "blue-to-red cycle", which in themselves don't really exist outside of the brain of a life-form that has evolved to conceptualized and assign stepped "color" to the sensory interpretation of electromagnetic cycling.

 

So, this is why it takes only about 50nm of bandwidth to yield a sufficient-enough color cycle / unit in terms of color interpretation, within the "UV-A" region.

 

And, as energy / wave-form frequency DECREASES to the right, this makes sense why it requires about roughly 300nm of bandwidth (from 400 to 700nm) to complete the next blue-to-red cycle / unit of color mapping (in the "visible"-assigned section of electromagnetism).

 

By stark contrast, then, if we were able to do blue-to-red color-mapped photography at even GREATER energies (with even TIGHTER wave-form frequencies), then the bandwidth required to yield yet another blue-to-red cycle / unit of color mapping would be even LESS wider (perhaps only 10nm to 15nm across, within the "UV-C" region, to yield a complete color profile/interpretation. Possibly even less, as we approach "X-ray" bands). With Gamma electromagnetism, it will take much less than even 1nm of bandwidth across, to obtain a simulated blue-to-red color mapping cycle / unit! In fact, we would be dealing with segments of "Am" units (ångström-meters), instead of "Nm" units (nano-meters), when measuring Gamma electromagnetism.

 

On the other extreme end (of progressively WEAKER energy), we would probably need to be able to photograph IR radiation as deeply as 5,000nm or possibly even 10,000 nm, in order to map a complete blue-to-red cycle / unit of color mapping, if measuring from the 700nm starting line! This explains why we cannot obtain "IR color" mapping with most "full-spectrum" converted cameras, and instead are treated to MONOTONE. The IR range is so weak of an energy (and the wave-form frequencies / wave-lengths so stretched out), that the typical 700 to 2,000nm range of most converted cameras does not provide a wide enough bandwidth for a complete unit of blue-to-red color mapping!

 

But, if we would have access to specialized cameras that CAN photograph IR into more deeper territories (5,000nm or deeper), then we would then have enough bandwidth in order to assign blue-to-red color mapping for IR (instead of being confined to monotone). At least, this is my understanding, anyway. Although I could be inaccurate.

 

Very interesting stuff, no? :rolleyes:

 

 

Plus there is the not entirely unimportant question of exposure time. I'm living in a Nordic region in which UV levels are fairly low so getting the most of what little UV is present the filter has its merits. On a good day I can even do UV handheld when a Baader U 2" is used.]It is true this filter is expensive. But when it can give you many years of service, the price is more agreeable. For an m43 camera in which you always use dedicated mount adapters, mounting the filter inside the adapter makes it far less prone to damage so its longevity is enhanced.

 

 

Agreed. Exposure time is the GREATEST advantage of a single, high-quality filter such as Baader-U. Which is yet ANOTHER primary reason why I have saved it for mostly INDOOR use, given that UV energy is a precious commodity when it comes to INDOOR UV work. It is certainly a more meticulous and involved process to obtain sufficient UV for adequate exposure, indoors. (Proper placement and positioning of full-spectrum Xenon flash tubes, for example. Or, alternatively, more dangerous and continuously emitting broad-spectrum UV bulbs, where it is mandatory for one to implement protective clothing, application of sunblock, and / or eye shielding).

 

 

Excellent points about setting up an internally-mounted filter, on the rear-element / sensor-facing side. I fully agree! I plan to implement such a set-up in the future, as well!

 

It should also be mentioned that an INTERNALLY-mounted filter will also drastically cut down on (if not eliminate) instances of internal reflections, flaring, ghosting, hot-spots, and other unwanted artifacts ... compared to a filter mounted on the FRONT of the lens, which is at the mercy of potentially harsh light angles from the external environment.

 

Of course, it is still wise to place a deeply-recessed hood on the front of the lens, nonetheless.

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Igor wrote: And typically, 340nm is the bottom-most norm, for many of the cheaper "UV accidents" of the 1940's through 1960's preset lenses for "regular" photography (before UV-blocking multi-coatings began to be used, in the late 60's / early 70's).

 

What's your reference for this statement, please??

 

*******

 

Igor wrote: Here is the approximate transmission bandwidth of stacking U-360 (2mm thick) with S8612 (1.5mm thick), supplied to me by a trusted merchant / supplier.

You can go onto the Schott site and get software to make charts like the one you posted.

Thus you can design your own combos of filters. It is interesting !!

 

The merchant appears to be uviroptics on Ebay. UV is a small world. Most of us "know" one another from encounters on forums, etc. ;)

 

******

 

Igor wrote: This is truly an unrivaled and robust system of in-camera custom white-balancing, as said above to Fierce Bear. It is very similar to the "click to white-balance" tools, in PP.

Yes, we are well aware of this having been through experiments with many, many converted cameras. :rolleyes:

 

The Panasonic M-4/3 systems can do it quite well, with no need for PP white-balancing.

They do pretty well. However, do take note that once your internal ICF is removed you might find in some cameras that the white balancing becomes a bit less accurate. And the saturations get thrown off a bit. So there frequently remains a need for proper colour profiling in the converter/editor.

And one encounters out-of-gamut colours in some flowers when using a converted cam for Visible reference shots - particularly the blue & violet flowers do not shoot always so well. So this has to be dealt with in editing anyway. Wish it were not so, but experience says differently.

 

The Lumix bodies are OK, but lack dynamic range and low light capability both of which I consider very important for what I try to do in UV photography. Of course, YMMV. Some of the Sonys and, of course, the Nikons are better in w.r.t dynamic range and low light and may be found on the used market.

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What's your reference for this statement, please??

 

It's based on my own experiences with "regular" (non quartz-fluorite) glass. I've never seen "regular" glass (composed of about 70% SiO2, then seeded with Na2O, MgO, and other additives) transmit any deeper (usefully) than roughly 340nm. Perhaps down to 325 or so, within STRONG uv-emitting environment. This "reference" is not PRECISE. I am just throwing around ESTIMATES / BALLPARK figures, here. ;)

 

(Whereas, we already know that fused-silica SiO2 and fluorite CaF2 lens elements can permit for much deeper transmissions).

 

I'm not a glass-baking/smelting expert by any means, but I am simply citing from my own experiences. Am I that way off the mark? :rolleyes:

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The merchant appears to be uviroptics on Ebay. UV is a small world. Most of us "know" one another from encounters on forums, etc. :rolleyes:

 

Correct. But I thought it polite to not peddle sources of goods, unless given express permission by both the merchant AND the forum admin. Is this not proper forum etiquette? Which is why I didn't list the supplier by name. And NOT because it is some sort of secrecy.

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They do pretty well. However, do take note that once your internal ICF is removed you might find in some cameras that the white balancing becomes a bit less accurate. And the saturations get thrown off a bit. So there frequently remains a need for proper colour profiling in the converter/editor.

And one encounters out-of-gamut colours in some flowers when using a converted cam for Visible reference shots - particularly the blue & violet flowers do not shoot always so well. So this has to be dealt with in editing anyway. Wish it were not so, but experience says differently.

 

And this is why I DO a lot of PP editing, anyway. Never said that I didn't. However, isn't it an advantage to be able to come as close to your desired results, IN-CAMERA, in order to cut down on workflow, in POST work? This has been my philosophy. :P

 

The Lumix bodies are OK, but lack dynamic range and low light capability both of which I consider very important for what I try to do in UV photography. Of course, YMMV. Some of the Sonys and, of course, the Nikons are better in w.r.t dynamic range and low light and may be found on the used market.

 

Well, apples and oranges, of course. I could just as well argue that you should just shoot in medium-format. Why not full-spectrum convert a $50,000 Hasselblad, while you're at it? It DOES, after all, have superior dynamic range to your Nikon or Canon, right? ;)

 

So you see ... point is, tools are tools. And abilities are all relative. And each system has advantages and disadvantages. No SINGLE system does it all best. Heck, even a fixed-lens COMPACT (point & shoot) model converted to full-spectrum is quite sufficiently handy, as a second-rate "tag along" tool, when you're out and about doing other things, and an opportunity suddenly presents itself.

 

I do have a higher-dynamic-range APS-C camera converted to full-spectrum, too. But that doesn't mean that I am going to lug around my "flagship" prized possession, everywhere I go ... including the supermarket, a business luncheon, a family gathering, or driving to work and back home. But then, that's MY lifestyle preference, of course. It doesn't necessarily mean that everyone else's has to be identical to mine. :rolleyes:

 

(If someone wants to eat, sleep, crap, and take long, candle-lit romantic baths with their Nikon D4, then who am I to stop them? Haha.)

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I have four (or five, if you include UV video): broadband D600, D200, GH-2*2, and D3200 with the Baader U 2" internally. The D200 now rarely sees use so perhaps should no longer be counted in. The D600 is used for much of the studio work and has its dedicated UV-Nikkor and studio flashes. The D3200 is a field kit outfitted with its own UV-Nikkor or a Noflexar 35. I'm using the SB-140 flash for this camera. Another SB-140 and the Coastal Optics 60 mm f/4 APO are allocated to one of the GH-2 units. This GH-2 is accompanied by a D300 with 120 mm f/4 Medical Nikkor for reference captures.

 

The second GH-2 is for video and hence uses any lens required for the actual shoot.

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Been thru the Nikon D70, D200, D300, D700 (huge bust!!), D7000, Lumix GH1 and something else I can't remember right now.

 

Currently using the Nikon D600 and Pentax K5 which provide flange focal distances for about half my lenses. Prolly need a Sony or another m/4/3 for some other lenses. We shall see.

 

I would like to play with medium format some day, but the UV lenses aren't there AFAIK except for the UV-Sonnar (??), but I'm not crazy about that lens and have not "collected" it.

 

OK, back to work for Annedi. :rolleyes:

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Actually I'm not sure the medium format digicams have dynamic range better than the D800, but I would have to go look that up.

someday, when I have more time. :rolleyes: They certainly don't have the high ISO capability. But likely make up for it in many other ways.

A converted Point-n-Shoot would indeed be fun for scouting UV shoots and for general fun stuff.

 

 

I am soooooooo behind. Really gotta get back to work now.

Bye all !!!

TTYL.

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You could easily mount the filter pack in an exchangeable unit, using say a K3 ring on the lens and K2 to hold the filters, Then you have a bayonet mount so swapping filters is a split-second affair. Provided you are careful you won't even need to twist the K2 so it locks thus avoiding the need for pushing the unlock tab when you want to get the filter off.

 

 

 

Bjørn,

Can you point to a retailer who has the K2/K3 rings in stock? - I couldn't find them, so far.

 

Thanks, Nico

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